Preparation method and application of super-hydrophobic and super-oleophylic sponge with photothermal effect

Abstract

The invention belongs to the field of oily wastewater treatment, and discloses a preparation method and application of super-hydrophobic and super-oleophylic sponge with a photothermal effect, and the preparation method comprises the following steps: step 1, preparing lignin microspheres; and step 2, preparing the lignin microsphere and candle ash nanoparticle modified super-hydrophobic polyurethane sponge. The preparation cost of the super-hydrophobic polyurethane material is greatly reduced, the lignin serving as a byproduct of the papermaking industry is extremely low in cost, and the candle ash nanoparticles are pollutants generated after candle combustion, so that the preparation cost can be reduced, and the problem of environmental pollution can be solved at the same time; pDMS is introduced as an adhesive, so that the use of fluorine-containing substances can be replaced to reduce environmental pollution, and PDMS is also beneficial to improving the adsorption capacity of oil, and is beneficial to efficient adsorption and separation of viscous crude oil.

Description

Technical Field

[0001] The invention belongs to the field of oily wastewater treatment, and specifically relates to a preparation method and application of a super-hydrophobic and super-oleophilic sponge with photothermal effect. Background Art

[0002] Polyurethane sponge is a commonly used sponge material with hydrophilic and oleophilic characteristics. It can be used to adsorb oily wastewater, but it cannot separate oil from wastewater. When polyurethane sponge is modified with micro-nano particles (or surface roughening) and treated with low energy (fluoride or other low energy compounds), it can be used to prepare super hydrophobic and super oleophilic sponge. Super hydrophobic polyurethane sponge can not only adsorb oil, but also repel water, thereby achieving effective oil-water separation.

[0003] Superhydrophobic polyurethane sponge can be used for oily wastewater treatment. For the separation of viscous oil (crude oil), the following problems currently exist:

[0004] (1) Photothermal effect. For the separation of viscous oil, it is necessary to introduce photothermal absorbing particles during the preparation of the superhydrophobic sponge. Under light, the viscosity of viscous oil (crude oil) decreases as the temperature increases. At this time, the superhydrophobic polyurethane sponge can efficiently adsorb and separate the viscous oil. Therefore, for crude oil separation, photothermal performance is what the superhydrophobic polyurethane sponge needs to have.

[0005] (2) Low-cost preparation. Currently, commonly used photothermal absorption particles include gold nanoparticles, carbon nanotubes, graphene, etc., which are relatively expensive. Therefore, the introduction of low-cost photothermal nanoparticles is of great significance for superhydrophobic sponges.

[0006] (3) Fluoride-free treatment of super-hydrophobic materials. For super-hydrophobic materials, it is very important not to use fluoride without affecting the super-hydrophobic performance, which can reduce the environmental pollution caused by fluoride. However, there are still many fluorine-containing super-hydrophobic materials.

[0007] (4) Efficient separation of viscous oil (crude oil). The separation of viscous crude oil is a difficult problem in the treatment of oily wastewater. How to use superhydrophobic materials to achieve repeatable and efficient recycling is very important. Therefore, when designing superhydrophobic materials, it is necessary to consider not only the realization of superhydrophobicity and recyclability, but also the improvement of crude oil adsorption capacity and adsorption efficiency.

[0008] In the preparation of superhydrophobic polyurethane, lignin, a by-product of the papermaking industry, and candle ash after burning candles are introduced to construct the rough structure of the polyurethane skeleton surface. At the same time, polydimethylsiloxane (PDMS) is introduced as an adhesive to achieve the fluorination-free superhydrophobic polyurethane. This study has not yet found this.

[0009] The technical problem, or technical difficulty, that needs to be solved at present is the ratio of lignin microspheres to candle ash nanoparticles: (1) If there are too many lignin microspheres and too few candle ash nanoparticles, the photothermal effect of the superhydrophobic polyurethane sponge will be poor, thereby affecting the adsorption and separation of viscous crude oil; (2) If there are too few lignin microspheres and too many candle ash nanoparticles, although the photothermal effect of the superhydrophobic polyurethane sponge will increase, many active groups of lignin microspheres (such as aromatic hydroxyl, methoxy, sulfonic acid, etc.) will be reduced, thereby affecting the adsorption capacity of viscous crude oil; (3) When the ratio of lignin microspheres to candle ash nanoparticles is appropriate, they can not only maximize the surface active groups, but also achieve photothermal synergistic effect, thereby promoting the efficient adsorption and separation of viscous crude oil. Summary of the invention

[0010] In order to solve the above technical problems existing in the prior art, the present invention provides a method for preparing a super-hydrophobic and super-oleophilic sponge with photothermal effect, comprising the following steps:

[0011] Step 1. Preparation of lignin microspheres

[0012] 1.1 Dissolve a certain mass of sodium lignin sulfonate powder in 10 g of deionized water to obtain a sodium lignin sulfonate solution;

[0013] 1.2 Dissolve 10 g of hexadecyltrimethylammonium bromide (CTAB) in a mixed solution of ethanol and water to form a CTAB solution;

[0014] 1.3 Mix the sodium lignin sulfonate solution and the CTAB solution and stir at 700 rpm for 30 minutes;

[0015] 1.4 Add 160 mL of deionized water dropwise into the above mixture at a rate of 3 mL / min and stir for 2 hours to obtain a stable colloidal system;

[0016] 1.5 The above colloidal system was washed with deionized water for 3 times at 5000 rpm for 5 min, and then dried to obtain lignin microspheres;

[0017] Step 2. Preparation of lignin microspheres and candle ash nanoparticles modified superhydrophobic polyurethane sponge

[0018] 2.1 Use scissors to cut the polyurethane sponge into small pieces with the same thickness;

[0019] 2.2 Dissolve a certain mass of PDMS prepolymer and PDMS curing agent in a certain volume of n-hexane at a ratio of 10:1 and stir thoroughly;

[0020] 2.3 Place ordinary glass above the lit candle to collect the soot, which is the candle ash nanoparticles, and calcine it at 200°C;

[0021] 2.4 Mix a certain amount of lignin microspheres and candle ash nanoparticles in the above solution and sonicate for 1 hour;

[0022] 2.5 Soak a clean polyurethane block sponge in the mixed solution in step 2.4, stir it thoroughly for 2 hours, and dry and cure the soaked polyurethane sponge at 120°C for 2 hours to obtain a superhydrophobic polyurethane sponge modified with lignin microspheres and candle ash nanoparticles and bonded with PDMS.

[0023] Furthermore, in the mixed solution of ethanol and water in step 1.2, the mass ratio of ethanol to water is 3:2.

[0024] Furthermore, in step 1.2, the CTAB mass fraction of the CTAB solution is 33.3%.

[0025] An application of the superhydrophobic and superoleophilic sponge with photothermal effect prepared by the above preparation method in the efficient adsorption and separation of viscous crude oil.

[0026] Beneficial Effects

[0027] (1) Greatly reduce the preparation cost of superhydrophobic polyurethane materials. Lignin is a byproduct of the papermaking industry and its cost is extremely low. Candle ash nanoparticles are pollutants after candle burning. Therefore, the introduction of two extremely low-cost nanomaterials can not only reduce the preparation cost, but also solve the problem of environmental pollution at the same time, achieving the goal of killing two birds with one stone.

[0028] (2) The introduction of PDMS as an adhesive can not only replace the use of fluorinated substances to reduce environmental pollution, but PDMS itself is also beneficial to increase the adsorption capacity of oil, which is conducive to the efficient adsorption and separation of viscous crude oil. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a flow chart of the preparation method of the super-hydrophobic and super-oleophilic sponge with photothermal effect of the present invention;

[0030] Figure 2 are scanning electron micrographs, including (a) untreated polyurethane sponge, (b) lignin microspheres, (c) candle ash nanoparticles, (d) and (e) superhydrophobic polyurethane;

[0031] Figure 3 It is a chemical structure characterization diagram, including (a), (b) XPS diagram, (c) XRD diagram, and (d) infrared diagram;

[0032] Figure 4 Schematic diagram of the wettability and self-cleaning properties of the superhydrophobic sponge;

[0033] Figure 5Schematic diagram of thermal stability, chemical stability and wear resistance of superhydrophobic sponge;

[0034] Figure 6 This is a schematic diagram of the adsorption performance and separation efficiency of superhydrophobic sponge for oil;

[0035] Figure 7 This is a schematic diagram of the photothermal effect of a superhydrophobic sponge;

[0036] Figure 8 This is a schematic diagram of the adsorption of crude oil by a superhydrophobic sponge;

[0037] Fig. 9 This is a schematic diagram of the dynamic adsorption of crude oil by superhydrophobic sponge. DETAILED DESCRIPTION

[0038] The present invention will be further described below in conjunction with the accompanying drawings.

[0039] like Figure 1 As shown, the preparation method of the super-hydrophobic and super-oleophilic sponge with photothermal effect of the present invention comprises the following steps:

[0040] Step 1. Preparation of lignin microspheres

[0041] 1.1 Dissolve a certain mass (0.5 g, 1 g, 1.5 g, 2 g, 2.5 g, 3 g, etc.) of sodium lignin sulfonate powder in 10 g of deionized water to obtain a sodium lignin sulfonate solution;

[0042] 1.2 Dissolve 10 g of hexadecyltrimethylammonium bromide (CTAB) in a mixed solution of ethanol and water (mass ratio 3:2) to form a CTAB solution (mass fraction 33.3%);

[0043] 1.3 Mix the sodium lignin sulfonate solution and the CTAB solution and stir at 700 rpm for 30 minutes;

[0044] 1.4 Add 160 mL of deionized water dropwise into the above mixture at a rate of 3 mL / min and stir for 2 hours to obtain a stable colloidal system;

[0045] 1.5 The above colloidal system was washed with deionized water for 3 times (5000 rpm, 5 min), and then dried to obtain lignin microspheres.

[0046] Step 2. Preparation of lignin microspheres and candle ash nanoparticles modified superhydrophobic polyurethane sponge

[0047] 2.1 Use scissors to cut the polyurethane sponge into 1cm×1cm size with the same thickness;

[0048] 2.2 Dissolve a certain amount of PDMS prepolymer (20 mg, 40 mg, 80 mg, 160 mg, 320 mg) and PDMS curing agent (2 mg, 4 mg, 8 mg, 16 mg, 32 mg) in a certain volume of n-hexane (10 mL, 20 mL, 30 mL, 40 mL, 50 mL, 60 mL) at a ratio of 10:1 and stir thoroughly.

[0049] 2.3 Place ordinary glass above the lit candle to collect the soot, which is the candle ash nanoparticles, and calcine it at 200°C;

[0050] 2.4 A certain amount of lignin microspheres (1 mg, 2 mg, 5 mg, 10 mg, 20 mg, 40 mg, 80 mg, etc.) and candle ash nanoparticles (1 mg, 2 mg, 5 mg, 10 mg, 20 mg, 40 mg, 80 mg, etc.) were mixed in the above solution and ultrasonicated for 1 hour;

[0051] 2.5 Soak a clean polyurethane block sponge in the mixed solution of (4), stir it thoroughly for 2 hours, and dry and cure the soaked polyurethane sponge at 120°C for 2 hours to obtain a superhydrophobic polyurethane sponge modified with lignin microspheres and candle ash nanoparticles and bonded with PDMS.

[0052] Micro-nanostructure characterization of superhydrophobic polyurethane sponge

[0053] like Figure 2 As shown in (a), the original polyurethane sponge skeleton surface is smooth and its diameter is about 100 to 700 μm; from (b), it can be seen that the diameter of the lignin microspheres is about 2-3 μm, and from (c), it can be seen that the diameter of the candle ash is about 50-80 nm. By mixing with the PDMS prepolymer, the lignin microspheres and candle ash can be easily modified to the skeleton of the polyurethane sponge, and after curing in the oven, the surface roughness of the polyurethane sponge is formed. From (d) and (e), it can be seen that the lignin microspheres are well dispersed in the PDMS layer, and the candle ash aggregates to form a microscale structure.

[0054] Chemical structure characterization of superhydrophobic polyurethane sponge

[0055] like Figure 3As shown, X-ray photoelectron spectroscopy (XPS) shows that the characteristic peaks at 284.8eV and 285.1eV in the C1s spectrum of the superhydrophobic polyurethane sponge correspond to CC and CO bonds (a), indicating that the lignin microspheres are successfully incorporated into the superhydrophobic sponge. In addition, the characteristic peaks at 532.8eV, 531.9eV, and 533eV correspond to CO, C=O, and Si-O bonds (b), respectively, which can be attributed to the modification of the polyurethane sponge by PDMS, lignin microspheres, and candle ash particles shown in the O1s spectrum. According to the X-ray diffraction (XRD) pattern (c), the broad diffraction peaks between 2θ=15° and 2θ=25° indicate the amorphous structure of the superhydrophobic sponge.

[0056] In addition, the infrared spectrum (d) specifically analyzes the chemical composition of the superhydrophobic sponge. For example, the characteristic peaks at 3286cm-1, 2870cm-1, 2968cm-1, 1714cm-1 and 1643cm-1 are attributed to the NH stretching and CH stretching of -CH and -CH. The peak at 1018cm-1 is due to the stretching vibration of the Si-O-Si chain in PDMS. In addition, the characteristic peak at 1508cm-1 is attributed to the vibration of the aromatic unit, the peak at 1261cm-1 is a sign of the guaiacyl unit in lignin, and the peak at 1058cm-1 is related to the stretching vibration of lignin CO.

[0057] Self-cleaning properties of superhydrophobic sponge

[0058] Figure 4 The wettability and self-cleaning properties of the superhydrophobic sponge are shown. For example, various droplets (i.e., milk, tea, coffee, orange juice, acidic solution, and alkaline solution) are placed on the superhydrophobic sponge, and the droplets are spherical (a). The superhydrophobic sponge is immersed in deionized water and simulated seawater, and there are many bubbles on the superhydrophobic surface (b), showing a silver mirror phenomenon, thereby proving the superhydrophobicity of the sponge surface. As shown in (c), the surface of the superhydrophobic sponge has very good water repellency. From (d), it can be seen that due to the low adhesion of water on the superhydrophobic surface, water droplets can be easily removed from the surface of the superhydrophobic sponge without any residue. In order to further verify the self-cleaning performance, different liquids (i.e., tea, coffee, milk, and orange juice) are poured on the superhydrophobic sponge (e). The experimental results show that the superhydrophobic sponge has excellent liquid repellency; at the same time, the surface of the superhydrophobic sponge after transverse cutting still shows superhydrophobicity (f), so it has potential application prospects in the fields of antifouling and self-cleaning.

[0059] To further test the wettability, the contact angles of different liquids (i.e., tea, cola, coffee, milk, orange juice, and yogurt) on the superhydrophobic surface ranged from 155.2° to 149.4°, and the corresponding sliding angles ranged from 1.8° to 7.6°, showing the excellent liquid repellency of the superhydrophobic sponge. As can be seen from (g), the superhydrophobic sponge can still maintain good surface superhydrophobicity after being immersed in muddy water for several cycles (h). When the surface superhydrophobic sponge is contaminated by solid particles, such as yellow chalk powder and SiO 2 The particles, after being rinsed with deionized water, have a clean surface again (i).

[0060] Thermal stability, chemical stability and wear resistance of superhydrophobic sponge

[0061] like Figure 5 As shown in (a), it can be seen that the superhydrophobic sponge is immersed in boiling water (100°C) for a certain period of time (0-180 minutes). After 30 minutes, the sponge still maintains the superhydrophobic surface contact angle; after 180 minutes, the contact angle decreases from 156.3° to 141.9°. The possible reason is that the micro / nanostructure on the sponge surface is gradually degraded in boiling water.

[0062] To evaluate the chemical stability, the contact angles of the superhydrophobic sponge were 149.9°, 150.9°, 148.5°, and 150.0°, respectively, after being immersed in various liquids (i.e., 1M NaCl, n-hexane, carbon tetrachloride, and ethanol) for 24 hours (b). The contact angle of the superhydrophobic sponge decreased from 154.8° to 141.1° and 140.9°, respectively, after being immersed in strong acidic (pH=1) and alkaline (pH=13) solutions for 25 hours (c). This is because the strongly corrosive solution can gradually penetrate into the micro / nanostructure on the superhydrophobic sponge skeleton, and the micro / nanostructure on its surface will gradually degrade over time. When the pH value of the corrosive solution changes, there is a certain relationship between the contact angle and the pH value of the superhydrophobic sponge after being immersed for 24 hours. The experimental results show that either strong acid solution or strong alkaline solution will have a negative impact on the contact angle of the superhydrophobic sponge (d). In addition, after the superhydrophobic sponge was immersed in a 5wt.% NaCl solution and continuously stirred (1000rpm) for 30 hours, the contact angle of the superhydrophobic sponge remained at 150.4°(e). This indicates that the superhydrophobic sponge has better tolerance to saline solution than in strong acidic solution and alkaline solution.

[0063] In addition to thermal and chemical stability, this study also explored mechanical stability, as shown in (f)-(i). After 30 cycles of wear test using sandpaper, the contact angle of the superhydrophobic sponge decreased from 156.3° to 143.5°. This is mainly because the micro / nanostructure on the superhydrophobic surface was gradually worn away by the sandpaper during the cyclic friction process. In order to further study the mechanical stability, this study conducted cyclic bending and compression tests on the superhydrophobic sponge. The experimental results showed that the contact angle of the superhydrophobic sponge changed from 156.3° to 145.3° and 146.2°, respectively. This is due to the gradual loss of the micro / nanostructure on the superhydrophobic sponge skeleton during the cyclic test. In addition, the bonding adhesion between the micro / nanostructure (i.e., lignin microspheres and candle ash particles) and the polyurethane sponge was characterized by using tape adhesion. As can be seen from (i), after 10 cycles of testing, the contact angle of the superhydrophobic sponge decreased from 156.3° to 150.6°. The experimental results show that the micro / nanostructure on the superhydrophobic surface has good adhesion.

[0064] Adsorption performance and separation efficiency of superhydrophobic sponge for oil

[0065] like Figure 6 To evaluate the adsorption capacity of the superhydrophobic sponge, various oils and organic liquids were used in this study, including edible oil, n-hexane, paraffin, polyethylene glycol (PEG), ethanol, isopropyl alcohol (IPA), n-butanol, ethylene glycol (EG), tetrahydrofuran (THF), dichloromethane (DCM), carbon tetrachloride (CCl 4 ). From (a), it can be seen that the adsorption capacity of the superhydrophobic sponge for these organic liquids is 29.1 g / g (practical oil) to 129.3 g / g (CCl 4 ). For n-hexane and CCl 4 For example, after 15 cycles of adsorption experiments, the superhydrophobic sponge 4 The adsorption capacity of superhydrophobic sponge for n-hexane decreased slightly from 129.3 g / g to 119.3 g / g; the adsorption capacity for n-hexane decreased from 37.8 g / g to 35.8 g / g, indicating that its adsorption performance is relatively stable. After 15 cycles of testing, the separation efficiency of superhydrophobic sponge for n-hexane decreased from 99.5% to 97.5%, and the separation efficiency for CCl 4 The separation efficiency of the superhydrophobic sponge decreased from 98.6% to 97.9% (c). These experimental results show that the superhydrophobic sponge has excellent cyclic stability in terms of adsorption capacity and separation efficiency in the oil-water separation process.

[0066] In order to investigate the relationship between chemical stability and separation efficiency, the superhydrophobic sponge was immersed in different liquids (i.e., water, 1 M HCl, 1 M NaOH, and 1 M NaCl) for 24 h. 4The separation efficiency remains above 98.1%. The relationship between the adsorption capacity of the superhydrophobic sponge and the density of the oil (or organic solvent) (i.e., CCl4, silicone oil, paraffin oil, and n-hexane) is also discussed. As can be seen from (e), the superhydrophobic sponge exhibits a higher adsorption capacity for high-density oils (or organic solvents) than for low-density oils, which is related to the adsorption amount and type of the oil (or solvent). In addition, the superhydrophobic sponge has a higher adsorption capacity for various other oils (or organic solvents) (i.e., crude oil, dichloromethane, chloroform, paraffin, soybean oil, CCl4, and n-hexane). 4 The separation efficiency of oil-containing wastewater (including n-hexane and n-hexane) is greater than 95.1% (f), showing great potential for separating various oily wastewaters.

[0067] Photothermal effect of superhydrophobic sponge

[0068] like Figure 7 As shown in (a), it can be seen that the superhydrophobic sponge shows very good UV absorption. In order to evaluate the photothermal performance, the maximum surface temperature of the superhydrophobic sponge reached 79.3°C under solar irradiation (1 sun). The experimental results show that the introduction of lignin microspheres (or candle ash nanoparticles) helps to increase the surface temperature, and there is a synergistic photothermal effect between lignin microspheres and candle ash nanoparticles. In addition, the change in the surface temperature of the superhydrophobic sponge is also related to the intensity of solar radiation. As the light intensity increases, the surface temperature of the superhydrophobic sponge increases from 52.2°C (0.5 sun) to 114°C (2 suns), see (c) and (e). These results show that the superhydrophobic sponge can effectively absorb solar energy and convert it into thermal energy, showing great potential in photothermal applications.

[0069] Generally speaking, photothermal heating stability plays a vital role in practical applications. In order to evaluate the photothermal stability, this study conducted 10 continuous cycle tests on the superhydrophobic sponge under solar irradiation (1 sun). From (d), it can be seen that the surface temperature of the superhydrophobic sponge is relatively stable, ranging from 77.2℃ to 79.2℃ in 10 cycle tests.

[0070] Adsorption of crude oil by superhydrophobic sponge

[0071] like Figure 8 As shown in the infrared thermal image (a), it can be seen that the superhydrophobic sponge can reach a surface temperature of 79.3°C under 1 sun illumination, thereby effectively adsorbing crude oil. When the superhydrophobic sponge is saturated with crude oil, the adsorbed crude oil can be easily squeezed out (b). In order to verify the recyclability of its crude oil adsorption, this study conducted 10 cycle tests on the adsorption capacity and separation efficiency of the superhydrophobic sponge. After 10 cycle tests, the adsorption capacity of the superhydrophobic sponge for crude oil decreased slightly from 49.3g / g to 47.2g / g (c), and its separation efficiency for crude oil decreased from 95.2% to 93.4% (d).

[0072] In order to simulate the actual separation of crude oil, this study used a vacuum pump to filter the crude oil. Under 1 sun, the superhydrophobic sponge can quickly adsorb the crude oil. The corresponding infrared thermal image shows that under the sun, the temperature of the superhydrophobic sponge surface is significantly higher than the temperature of the crude oil and surrounding objects (e).

[0073] Dynamic adsorption of crude oil by superhydrophobic sponge

[0074] like Fig. 9 As shown in (a), it can be seen that the viscosity of crude oil decreases significantly with increasing temperature (its viscosity increases from 130.4 mPa·s (20℃) to 4.6 mPa·s (80℃). For the superhydrophobic sponge, its adsorption capacity for crude oil changes from 0 g / min at 20℃ to 12.5 g / min at 70℃ (b). In order to further study the adsorption process of crude oil, this study applied the first-order kinetic model and calculated q e The value is 51.9 g / g, and the k1 value is 0.09 (c). The experimental results show that under solar irradiation (1 sun), the superhydrophobic sponge can achieve saturated adsorption of crude oil within 35 seconds.

[0075] In addition, as can be seen from (d), under sunlight, the original polyurethane sponge can absorb a drop of crude oil (~500μL) within 750 seconds. In the absence of light, the superhydrophobic sponge takes 180 seconds to complete the same process (e); under light, the superhydrophobic sponge can quickly complete the above experimental process in just 16 seconds (f).

[0076] The preparation method of the super-hydrophobic polyurethane sponge can not only solve the four difficulties, but also solve the potential pollution problems caused by lignin and candle ash pollutants, which are byproducts of the papermaking industry, thereby achieving the purpose of high value-added utilization of lignin byproducts and candle ash waste. In addition, the super-hydrophobic polyurethane prepared by this technology can achieve efficient adsorption and separation of viscous crude oil, providing a feasible solution for offshore crude oil spills.

Claims

1. A method for preparing a super-hydrophobic and super-oleophilic sponge with photothermal effect, characterized by comprising the following steps: Step 1. Preparation of lignin microspheres 1.1 Dissolve a certain mass of sodium lignin sulfonate powder in 10 g of deionized water to obtain a sodium lignin sulfonate solution; 1.2 Dissolve 10 g of hexadecyltrimethylammonium bromide (CTAB) in a mixed solution of ethanol and water to form a CTAB solution; 1.3 Mix the sodium lignin sulfonate solution and the CTAB solution and stir at 700 rpm for 30 minutes; 1.4 Add 160 mL of deionized water dropwise into the above mixture at a rate of 3 mL / min and stir for 2 hours to obtain a stable colloidal system; 1.5 The above colloidal system was washed with deionized water for 3 times at 5000 rpm for 5 min, and then dried to obtain lignin microspheres; Step 2. Preparation of lignin microspheres and candle ash nanoparticles modified superhydrophobic polyurethane sponge 2.1 Use scissors to cut the polyurethane sponge into small pieces with the same thickness; 2.2 Dissolve a certain mass of PDMS prepolymer and PDMS curing agent in a certain volume of n-hexane at a ratio of 10:1 and stir thoroughly; 2.3 Place ordinary glass above the lit candle to collect the soot, which is the candle ash nanoparticles, and calcine it at 200°C; 2.4 Mix a certain amount of lignin microspheres and candle ash nanoparticles in the above solution and sonicate for 1 hour; 2.5 Soak a clean polyurethane block sponge in the mixed solution in step 2.4, stir it thoroughly for 2 hours, and dry and cure the soaked polyurethane sponge at 120°C for 2 hours to obtain a superhydrophobic polyurethane sponge modified with lignin microspheres and candle ash nanoparticles and bonded with PDMS.

2. The method for preparing a super-hydrophobic and super-oleophilic sponge with photothermal effect as claimed in claim 1, characterized in that: In step 1.2, the mass ratio of ethanol to water in the mixed solution of ethanol and water is 3:

2.

3. The method for preparing a super-hydrophobic and super-oleophilic sponge with photothermal effect as claimed in claim 1, characterized in that: The CTAB mass fraction of the CTAB solution in step 1.2 is 33.3%.

4. An application of a super hydrophobic and super oleophilic sponge with photothermal effect prepared by the preparation method as claimed in any one of claims 1 to 3 in the efficient adsorption and separation treatment of viscous crude oil.

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